Nonlinear regression for analysis of the uptake of KMnO4 from aqueous solutions onto natural marl

The present work aims to evaluate the performance of raw marl collected from the region of Oum El Bouaghi on the elimination of KMnO4 from aqueous solution. The adsorption capacities were studied using the batch technique as a function of pH, initial concentration and temperature. The maximum adsorption for KMnO4 was found to be 83.517% at pH 3.0. When the pH is low (pH<3.0), the uptake of KMnO4 occurs with an electrostatic attraction between the MnO4-ions and the surface proton groups, while at pH ≥3.0-8.0, the formation of complexes with the surface functional groups during the adsorption process and/or cation exchange are responsible for retention of Mn(II) ions onto marl. Experimental adsorption data were modeled with different nonlinear isotherms and kinetic models. Furthermore, statistical errors (SSE, SD, ARE, χ 2, R2 and R2 adj) were calculated to choose the suitable model. Langmuir isotherm was found to be best for fitting the experimental data. The calculated thermodynamic parameters indicated that adsorption process was physical, spontaneous and endothermic in nature. From this work, it was concluded that the natural marl can be used for effective elimination of KMnO4 from aqueous solution and wastewater.

Elucidation of Adsorption Mechanisms And Mass Transfer Controlling Resistances During Single And Binary Adsorption of Caffeic And Chlorogenic Acids

In this work, the potential of activated carbon to remove caffeic and chlorogenic acids was investigated. The study focused on evaluating the single and binary adsorption equilibrium, as well as investigating the mass transfer resistances present during the process by applying kinetic and diffusional models for a future scale-up of the process. For both compounds, the single adsorption equilibrium was studied at pH values of 3, 5, and 7. The experimental adsorption isotherms were interpreted using the Langmuir and Freundlich models, obtaining maximum adsorption capacities of 1.33 and 1.62 mmol/g for caffeic and chlorogenic acid, respectively. It was found that the adsorption mechanisms for both compounds was derived from π-π and electrostatic interactions. Also, the binary adsorption equilibrium was performed and the experimental data were interpreted using the extended multicomponent Langmuir model. The results evidenced that the binary adsorption of caffeic acid and chlorogenic acid is antagonistic in nature. The application of the first and second order kinetic models showed that the latter interpreted better the experimental data, obtaining R2 values close to one. Finally, the experimental adsorption rate data were interpreted by a diffusional model, finding the presence of different mass transfer resistances during the adsorption process. For both compounds, intraparticle diffusion mechanisms were meaningful.

Research of the adsorption of a methylene blue enterosorbents of various nature

The results of the adsorption study of methylene blue dye as the low molecular weight toxins marker from its aqueous solutions by carbon, silicon and polymer enterosorbents are presented. It has been shown that the activated carbons modification by water-soluble cellulose polyelectrolyte makes it possible to increase their adsorption capacity. The applicability of Langmuir, Freundlich, Temkin and Redlich – Peterson adsorption models for the approximation of experimental adsorption isotherms of methylene blue on the enterosorbents has been estimated. It has been established that the three-parameter Redlich – Peterson equation describes this process better than others. This was evident from the comparison of the regression coefficients, constants and parameters values of these equations.

Assessing in Silico Models and Methods for Non-Covalent Interactions between Graphene and Small Molecules

<p><a>Designing and optimising graphene-based gas sensors, which involve physisorption of analytes on the sensor surface, requires theoretical insights into the strength and nature of such non-covalent interactions. This modelling entails constructing appropriate atomistic representations for an infinite graphene sheet and its complex with the analyte, then selecting accurate yet affordable methods for geometry optimisations and energy computations. In this work, density functionals from the 2^nd to 5^th rungs of Jacob’s ladder, coupled cluster theory, and symmetry-adapted perturbation theory in conjunction with a range of surface models, from benzene to the periodic system, were tested for their ability to reproduce experimental adsorption energies of CO₂ on graphene in a low-coverage regime. The best agreement with the reference computations was found for global and double hybrid density functionals, while experimental adsorption energies were reproduced within chemical accuracy by extrapolating the SAPT0//DSD-BLYP-D3 interaction energies from finite clusters to infinity</a>. This simple yet powerful extrapolation scheme effectively removes size dependence from the data obtained using finite cluster models, and the latter can be treated at more sophisticated levels of theory relative to periodic systems.</p>

Assessing in Silico Models and Methods for Non-Covalent Interactions between Graphene and Small Molecules

<p><a>Designing and optimising graphene-based gas sensors, which involve physisorption of analytes on the sensor surface, requires theoretical insights into the strength and nature of such non-covalent interactions. This modelling entails constructing appropriate atomistic representations for an infinite graphene sheet and its complex with the analyte, then selecting accurate yet affordable methods for geometry optimisations and energy computations. In this work, density functionals from the 2^nd to 5^th rungs of Jacob’s ladder, coupled cluster theory, and symmetry-adapted perturbation theory in conjunction with a range of surface models, from benzene to the periodic system, were tested for their ability to reproduce experimental adsorption energies of CO₂ on graphene in a low-coverage regime. The best agreement with the reference computations was found for global and double hybrid density functionals, while experimental adsorption energies were reproduced within chemical accuracy by extrapolating the SAPT0//DSD-BLYP-D3 interaction energies from finite clusters to infinity</a>. This simple yet powerful extrapolation scheme effectively removes size dependence from the data obtained using finite cluster models, and the latter can be treated at more sophisticated levels of theory relative to periodic systems.</p>

Adsorption of Sodium Cholate on Cationic Dextran Gels: Comparison of Isotherm Binding Models

Cationic dextran hydrogels having pendent 51-59 mol% N-alkyl-N,N-dimethylammonium chloride groups were synthesized and tested as adsorbents for sodium cholate. The bile acid salt sorption by these gels was evaluated by equilibrium analysis in water and 10 mM NaCl solution. The best adsorption results were obtained with amphiphilic dextran-based gels having two types of pendant ammonium chloride groups with different polarities. Experimental adsorption data for all polymers fitted good with Langmuir, Dubinin-Raduskevich and Temkin models over the entire range of ligand concentrations. The maximum experimental adsorption capacity of dextran sorbents for sodium cholate was in the range 850-1075 mg/g.

Development and Characterization of Iron Coated Chitosan Beads (ICCB) to remove Arsenic from Groundwater

The current situation of Pakistan is reaching to an alarming situation in the context of polluting water bodies as well as groundwater due to various natural and anthropogenic activities, which can be foreseen for shortage and unavailability of safe and healthy drinking water for the population. The greater part of Pakistani individuals (almost 60%) living underneath the neediness line so they don't move toward perfect and safe drinking water supplies. Arsenic is one of the hazardous metals presents in various territories of Pakistan as well as in various zones of the world. Its essence strokes individuals' wellbeing by sullying the water. This experimental adsorption study emphasizes on the arsenic removal from drinking water by utilizing cost-effective adsorbent called "Iron Coated Chitosan Beads (ICCB)". This technique is more useful and effective when contrasted with different removal methodologies to remove arsenic from groundwater. ICCB was utilized and it was discovered a compelling and productive adsorbent for the removal of arsenic from groundwater. From all clump tests, the removal level of arsenic is achieved from 79 % to 98%. These results demonstrated that ICCB can be utilized as a productive adsorbent material for the removal of arsenic from water.